1     Scope 
 2     References 
 3     Terminology     
 4     Abbreviations   
 5     Public data transmission services  
        5.1     General aspects of data transmission services         
        5.2     Technical characteristics of circuit switched data transmission services         
        5.3     Technical characteristics of packet switched data transmission services provided by PSPDN or ISDN    
        5.4     Technical characteristics of frame relay data transmission services provided by FRPDN    
        5.5     Interworking between PDNs and the Internet         
 6     Optional user facilities      
        6.1     Data transfer related facilities          
        6.2     Facilities to convey user data other than during the data transfer phase        
        6.3     Addressing related facilities
        6.4     Routing related facilities      
        6.5     Charging related facilities    
        6.6     Protection related facilities  
        6.7     Data link layer capabilities  
        6.8     Multipoint related facilities  
        6.9     Other optional user capabilities/facilities